Vehicle roadways commonly employ a guardrail assembly as a safety barrier for vehicles. Guardrail assemblies are known to include guardrail sections joined together and supported at a predetermined elevation adjacent the roadway surface. Guardrail assemblies commonly include a support assembly to support the guardrail sections at the predetermined elevation. One conventional support assembly includes a cylindrical wooden post and a mounting block for positioning between a guardrail and the cylindrical wooden post. However, certain mounting block structures may not provide a desired level of stability at the interface between the mounting block and cylindrical wooden post.